Organic EL displays can be broadly classified, according to methods with which their organic light-emitting layers are formed, into the following two types. One type employs a method of forming an organic light-emitting layer by deposition, which is used in the case where the organic light-emitting layer is made of a low-molecular-weight organic material. The other type employs a method of forming an organic light-emitting layer by a solvent coating method, which is often used in the case where the organic light-emitting layer is made of a polymeric organic material as well as a low-molecular-weight organic material.
As one of representative measures for forming an organic light-emitting layer by a solvent coating method, there is a method of discharging droplets of ink containing an organic light-emitting material into pixel regions of a display substrate using an ink jet device to form an organic light-emitting layer (see Patent Document 1). In the discharged droplet, an organic light-emitting material and a solvent are included.
The ink jet device includes an ink jet head having two or more nozzles. While controlling a positional relationship between the nozzles of the ink jet head and the display substrate, the ink jet device discharges ink from the nozzles. It is known that there are variations in size among droplets discharged from nozzles that the ink jet head has (see Patent Document 2). Reported in Patent Document 2 is a technique of causing a plurality of droplets to land on one pixel region and adjusting the landing position of each droplet, thereby improving film uniformity in the pixel region.
On the other hand, a pixel region of a display substrate into which droplets are discharged is often defined by a partition, referred to as a “bank”. This is for the purpose of causing discharged ink to position-selectively remain in the pixel region. A plurality of pixels are arranged on the substrate in rows of respective colors (R, G or B) such that they form a stripe pattern. As one of methods of discharging droplets onto a display substrate having banks that partition pixels, a method of discharging droplets while causing an ink jet head of an ink jet device to scan in a direction perpendicular to the longitudinal direction of the stripe is known (see Patent Documents 4 to 6).
Further, as another of the methods of discharging droplets onto a display substrate having banks that each partition pixels, a method of combining an ink jet head of an ink jet device that scans in a direction perpendicular to the longitudinal direction of the stripe and an ink jet head of the ink jet device that scans in the longitudinal direction of the stripe so as to apply droplets is known (see Patent Document 7).
On the other hand, banks may define a linear region including a group of pixels of the same color (for example, R: red, G: green, or B: blue) arranged in a row, among pixels arranged in the form of stripes (see Patent Document 3). The bank that defines the linear region may be referred to as a “linear bank”. That is, an organic light-emitting layer of R, G or B is formed in every region (hereinafter also referred to as a “linear region”) defined by the linear bank.